| 摘要 |
PURPOSE:To reduce a residual stress of a weld zone by providing an additional torch and executing heating from the peripheral side part of a pipe body, when a welding torch is positioned at the upper half part of the pipe body to be welded. CONSTITUTION:Welding is executed by making the end parts of two pipe bodies 7, 8 abut on each other, and moving a welding torch along its joint line 9. In this case, when the torch 4 is positioned on the upper half part of the pipe bodies 7, 8, heating of cooling water W is executed through the pipe wall by providing an additional torch 10 on the peripheral side part of the pipe bodies 7, 8. By heating the additional torch 10, circulating flows 11, 13 are generated, and a vapor phase of the uppermost part of the pipe body is made to flow. Accordingly, the colling efficiency of this part is improved, and a residual stress value can be reduced. |
